Display panel manufacturing method, display panel manufacturing apparatus, and display panel

ABSTRACT

A liquid crystal panel  11  includes a pair of substrates  18, 19 , liquid crystal  20  disposed between the substrates  18, 19 , and alignment films  30, 36  provided on the opposed surfaces of the substrates  18, 19 . After formation of the alignment film  30  or  36  is completed in a manufacturing process, it is checked by an inspection process whether a pinhole H is formed on the alignment film  30, 36 , and further the position of the pinhole H is detected. Thereafter, an alignment film repair filler  50  is applied to the pinhole H by a repair process, so that the pinhole H is repaired.

CROSS REFERENCE TO RELATED APPLICATION

This application is a Continuation of Ser. No. 12/234,086, filed Sep.19, 2008, which is a Continuation of National Phase PCT/JP2007/054718,filed Mar. 9, 2007, which designates the United States, which claimspriority on JP 2006-136899, filed May 16, 2006, the entire contents ofwhich are all hereby incorporated herein by reference in thisapplication.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a display panel manufacturing method, adisplay panel manufacturing apparatus, and a display panel.

2. Description of the Related Art

A liquid crystal panel, as a main component of a liquid crystal displaydevice, generally has a construction in which liquid crystal is disposedbetween a pair of glass substrates. TFTs as active devices, pixelelectrodes and the like are provided on the inside surface of one of theglass substrates, while a color filter, an opposite electrode and thelike are provided on the inside surface of the other of the glasssubstrates. An alignment film for alignment control of the liquidcrystal molecules is formed on the surface of each glass substrate thatis in contact with the liquid crystal.

A construction described in JP-A-2005-106997 is known as an example of aliquid crystal panel that includes alignment films.

Pinholes may be locally developed on the above-described alignment filmsfor the following reasons.

(1) When a foreign substance slips in during an alignment-film-formingprocess so as to adhere to the alignment film, the alignment film islocally removed due to elimination of the foreign substance, resultingin a pinhole.

(2) When adhesion of an alignment film to its underlying base (e.g.,pixel electrodes or an opposite electrode) is locally degraded, thealignment film material at the degraded portion is repelled during filmformation, resulting in a pinhole.

(3) When an alignment film material for vertical alignment of liquidcrystal molecules is used, adhesion of the alignment film to itsunderlying base is prone to degradation, which combined with the above(2) would cause a pinhole.

(4) When an alignment film having an uneven surface is formed byproviding depressed portions or raised portions on the underlying baseof the alignment film in order to control the alignment of the liquidcrystal molecules, a larger area of the underlying base is covered withthe alignment film, which combined with the above (2) would cause apinhole.

If pinholes are locally developed on the alignment film for the abovereasons, images cannot be displayed properly at those portions. Then,the alignment film should be completely removed and re-formed, dependingon the sizes and/or positions of the pinholes. These problems result inincrease in manufacturing cost.

SUMMARY OF THE INVENTION

The present invention was made in view of the foregoing circumstances,and an object thereof is to reduce manufacturing cost.

According to the present invention, in a process for manufacturing adisplay panel in which liquid crystal is disposed between a pair ofsubstrates arranged opposite to each other and an alignment film isprovided on an opposed surface of the substrates, a display panelmanufacturing method includes inspecting the alignment film for thepresence of a film defective part by an inspection process, detectingthe position of the film defective part by a position detection process,and applying an alignment film repair filler to at least a portion ofthe film defective part by a repair process so as to repair the filmdefective part.

A display panel manufacturing apparatus according to the presentinvention, which is a manufacturing apparatus for a display panel inwhich liquid crystal is disposed between a pair of substrates arrangedopposite to each other and an alignment film is provided on an opposedsurface of the substrates, includes an inspection means arranged toinspect the alignment film for the presence of a film defective part, aposition detection means arranged to detect the position of the filmdefective part, and a filler application means arranged to apply analignment film repair filler to at least a portion of the film defectivepart so as to repair the film defective part.

A display panel according to the present invention includes a pair ofsubstrates arranged opposite to each other, liquid crystal disposedbetween the substrates, an alignment film provided on an opposed surfaceof the substrates, and a repair part in which an alignment film repairfiller is applied to at least a portion of a film defective partdeveloped on the alignment film.

According to the construction, when a film defective part is detected byan inspection process, the position of the film defective part isdetected by the following position detection process. Thereafter, analignment film repair filler is applied to at least a portion of thefilm defective part by a repair process, so that the film defective partis repaired. Thereby, the yield rate can be improved, compared to theconventional case where an alignment film including a film defectivepart is re-formed, for example.

According to some aspects of the present invention, the followingpreferable constructions are provided.

(1) A stamping technique is used in the repair process of the displaypanel manufacturing method, so that the alignment film repair filler istransferred to the film defective part from a transfer means to whichthe alignment film repair filler is attached. Further, the fillerapplication means of the display panel manufacturing apparatus includesa transfer means arranged to transfer the alignment film repair fillerto the film defective part. Thereby, the film thickness of the repairpart can be readily adjusted, compared to the case where a technique fordropping droplets of an alignment film repair filler into a filmdefective part is used in a repair process, for example.

(2) In the repair process of the display panel manufacturing method, atransfer head, to which the alignment film repair filler is attached, ispressed to the film defective part in order to transfer the alignmentfilm repair filler. Further, the transfer means of the display panelmanufacturing apparatus includes a transfer head, to which the alignmentfilm repair filler is attached, and which is pressed to the filmdefective part. Thereby, the film thickness of the repair part can bereadily adjusted by controlling the duration time and/or the pressureintensity when the transfer head is pressed to the film defective part.Further, a locally-developed film defective part can be readilyrepaired, compared to the case where the transfer of an alignment filmrepair filler is achieved by a transfer roller, for example.

(3) The alignment film repair filler used in the display panelmanufacturing method is formed by dissolving an alignment film materialin solvent, and the transfer head after finishing repair waits whilebeing immersed in the alignment film repair filler. Further, the displaypanel manufacturing apparatus includes a dryness prevention means, inwhich the alignment film repair filler formed by dissolving an alignmentfilm material in solvent is stored, and which is capable of containingthe transfer head that is waiting after finishing repair. Thereby,drying of the surface of the transfer head due to evaporation of thealignment film repair filler can be prevented after the repair isfinished.

(4) The transfer head used in the display panel manufacturing method isformed of a porous material having flexibility. Further, the transferhead of the display panel manufacturing apparatus is formed of a porousmaterial having flexibility. Thereby, the film thickness of the repairpart can be further readily adjusted. Further, the alignment film repairfiller can be reliably applied to the film defective part due todeformation of the flexible transfer head, even if a stepped area isformed around the film defective part.

(5) A surface modification process for facilitating adhesion of thealignment film repair filler to the film defective part is performedbefore the repair process of the display panel manufacturing method.Further, the display panel manufacturing apparatus includes a surfacemodification means arranged to modify the surface of the film defectivepart in order to facilitate adhesion of the alignment film repair fillerto the film defective part. Thereby, the repair can be reliablyachieved, because the alignment film repair filler can easily adhere tothe film defective part in the repair process.

(6) Ultraviolet light is radiated to the film defective part in thesurface modification process of the display panel manufacturing method.Further, the surface modification means of the display panelmanufacturing apparatus includes an ultraviolet radiator arranged toradiate ultraviolet light to the film defective part. Thereby, thesurface modification can be suitably achieved by radiating ultravioletlight to the film defective part. Further, the processing time can bereduced, compared to the case where the surface modification is achievedby a wet process, for example.

(7) The ultraviolet light is radiated at a wavelength of 146 nm to 365nm in the display panel manufacturing method. Further, the ultravioletradiator of the display panel manufacturing apparatus radiates theultraviolet light at a wavelength of 146 nm to 365 nm. Thereby, thesurface modification of the film defective part can be further suitablyachieved.

(8) The alignment film of the display panel has a function for aligningliquid crystal molecules in a direction substantially perpendicular to asurface of the alignment film when a voltage is not applied to theliquid crystal. In the case of the alignment film thus having theso-called vertical alignment function, its adhesion to the substrate maybe degraded, and therefore a film defective part can be easily formedduring the manufacture thereof. However, the alignment film repairfiller can be applied to the film defective part so as to form therepair part. Thus, the film defective part can be repaired so that theyield rate is effectively improved.

(9) An uneven portion for alignment control of the liquid crystal isprovided on a surface of the substrates of the display panel, and thealignment film is formed along the uneven portion. In the case that theuneven portion is thus formed on the surface of the substrate, a largerarea of the substrate may be covered with the alignment film, andtherefore a film defective part can be easily formed. However, thealignment film repair filler can be applied to the film defective partso as to form the repair part. Thus, the film defective part can berepaired so that the yield rate is effectively improved.

(10) The film thickness of the repair part of the display panel is setto between 50 nm and 200 nm. Thereby, excellent display performance canbe obtained.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages of the present invention will become moreapparent from the following detailed description made with reference tothe attached drawings. In the drawings:

FIG. 1 is a sectional view of a liquid crystal display device accordingto an embodiment of the present invention;

FIG. 2 is an enlarged plan view of an array substrate;

FIG. 3 is an enlarged sectional view of a liquid crystal panel;

FIG. 4 is a schematic side view of an inspection/repair apparatus;

FIG. 5 is a block diagram of the inspection/repair apparatus;

FIG. 6 is a diagram showing a container for holding a transfer headtherein;

FIG. 7 is a sectional view showing when a foreign substance is adherentto a substrate;

FIG. 8 is a sectional view showing when a pinhole on the CF substrate isirradiated with excimer UV light;

FIG. 9 is a sectional view showing when the transfer head is positionedto be aligned with the pinhole;

FIG. 10 is a sectional view showing when the transfer head is pressed tothe pinhole;

FIG. 11 is a sectional view showing when an alignment film repair filleris attached to the pinhole;

FIG. 12 is a sectional view showing when the transfer head is pressed toa pinhole smaller than the transfer head;

FIG. 13 is a sectional view showing when an alignment film repair filleris attached to the pinhole smaller than the transfer head and to thealignment film;

FIG. 14 is a sectional view showing when a pinhole on the arraysubstrate is irradiated with excimer UV light;

FIG. 15 is a sectional view showing when the transfer head is positionedto be aligned with the pinhole;

FIG. 16 is a sectional view showing when the transfer head is pressed tothe pinhole; and

FIG. 17 is a sectional view showing when an alignment film repair filleris attached to the pinhole.

DETAILED DESCRIPTION OF THE INVENTION Embodiment

An embodiment according to the present invention will be explained withreference to FIGS. 1 through 17. A liquid crystal panel 11 included in aliquid crystal display device 10 will be illustrated in the presentembodiment. In the following explanations, the lower side of FIG. 1 isreferred to as the back side, while the upper side thereof is referredto as the front side.

First, the construction of the liquid crystal display device 10 will beexplained. As shown in FIG. 1, the liquid crystal display device 10generally has a construction, in which a liquid crystal panel 11 forimage display and a backlight 12 arranged as an external light source onthe back side (or rear side) of the liquid crystal panel 11 are fixed toeach other. The liquid crystal panel 11 is held so as to be sandwichedbetween the back-side backlight 12 and a bezel 13 that has asubstantially frame-like shape and is arranged on the front side (oranterior side).

The backlight 12 includes a casing 14 having a substantially box-likeshape with a front-side (i.e., liquid crystal panel 11 side) opening, aplurality of linear light sources 15 (e.g., cold cathode tubes) arrangedparallel to one another in the casing 14, a plurality of optical sheets16 arranged in a stack (e.g., a diffuser plate, a diffusing sheet, alens sheet and a brightness enhancement sheet, arranged in this orderfrom the back side) in the opening of the casing 14, and a substantiallyrectangular-shaped frame 17 for holding the optical sheets 16 togetherwith the casing 14 and therebetween. The optical sheets 16 have afunction for converting light from each linear light source 15 into flatlight, and the like.

Next, the liquid crystal panel 11 will be explained in detail. Theliquid crystal panel 11 generally includes a pair of transparent (orlight transmissive) glass substrates 18, 19, and liquid crystal 20disposed between the substrates 18, 19 as a material with an opticalproperty that changes with applied voltage. The substrates 18, 19 areattached to each other so as to face each other, while a predetermineddistance (or gap) is kept therebetween due to spacers not shown. Theliquid crystal 20 therebetween is held in a liquid tight state by asurrounding sealant 21. A pair of front and back polarizing plates 22,23 are attached on the outer surface sides of the respective substrates18, 19.

The front-side one of the substrates 18, 19 is provided as a CFsubstrate 18, while the back-side one thereof is provided as an arraysubstrate 19. On the inner surface side (i.e., liquid crystal 20 side orCF substrate 18 facing surface side) of the array substrate 19, as shownin FIG. 2, a large number of switching elements 24 (e.g., TFTs) andpixel electrodes 25 are arranged, and further source wiring lines 26 andgate wiring lines 27 are arranged in a grid pattern so as to surroundthe switching elements 24 and the pixel electrodes 25. The source wiringline 26 and the gate wiring line 27 are connected respectively to thesource electrode and the gate electrode of the switching element 24,while the pixel electrode 25 is connected to the drain electrode of theswitching element 24. As shown in FIG. 3, insulating layers 28, 29 areprovided in a stack between the pixel electrodes 25 and the arraysubstrate 19 or the wiring lines 26, 27.

Each pixel electrode 25 is formed of ITO (Indium-tin-oxide), forexample, so as to have a substantially rectangular shape elongated alongthe extending direction of the source wiring lines 26, as shown in FIG.2. An alignment film 30 for directional alignment of the liquid crystal20 is provided on the pixel electrodes 25 and on the inner surface sideof the outer insulating layer 29 (i.e., provided between the liquidcrystal 20 and the pixel electrodes 25 or the insulating layer 29). Thealignment film 30 is formed of a so-called vertical alignment typematerial (e.g., polyimide), so as to align the liquid crystal moleculesin a direction perpendicular to the surface of the alignment film 30when a voltage is not applied to the liquid crystal 20. The filmthickness of the alignment film 30 is set to about 100 nm to 200 nm, forexample. In the present embodiment, the pixel electrodes 25 and theinsulating layer 29 are thus provided as the underlying base for thealignment film 30. However, in a liquid crystal panel having anotherstack structure, a layer provided as the underlying base may differ fromthe above.

Slits 31 (corresponding to a groove, an opening or an uneven portion)are provided on the pixel electrode 25 (or on the surface of the arraysubstrate 19), so that the alignment film 30 formed along the pixelelectrode 25 has an uneven surface. Specifically, each slit 31 is formedas a groove-like depression having a predetermined width, and is locatedat the longitudinal center position of the pixel electrode 25, at aposition around either longitudinal end thereof, or at an intermediateposition therebetween. The slit 31 at the intermediate position isV-shaped when viewed from the top. The slit 31 at the center position isarranged on the side edge of the pixel electrode 25, and is triangularshaped when viewed from the top. The slit 31 at each end side forms alinear shape substantially parallel to the center-side slit 31. Theslits 31 are arranged substantially evenly spaced apart. By the unevenportions formed on the alignment film 30 due to the slits 31, thealignment of the liquid crystal molecules can be controlled so that theyform an angle with the vertical direction in FIG. 3 (i.e., with thedirection perpendicular to the surfaces of the substrates 18, 19).Consequently, a rubbing process conventionally performed for thealignment film 30 can be eliminated. The depths of the slits 31 are setso that they reach the insulating layer 29.

The source terminal portion and the gate terminal portion formed on theends of the respective source wiring lines 26 and gate wiring lines 27are arranged on an end portion of the array substrate 19. The one endside of a thin-film driver (electronic component) such as SOF (System OnFilm) is connected to each of the terminal portions via an ACF(Anisotropic Conductive Film) by clamping connection. A printed boardconnected to an external circuit is connected to the other end side ofthe SOF via an ACF by clamping connection.

On the other hand, as shown in FIG. 3, a large number of color filters32 are arranged on the inner surface side (i.e., liquid crystal 20 sideor array substrate 19 facing surface side) of the front-side CFsubstrate 18, so as to correspond to the respective pixel electrodes 25.Each color filer 32 has a function for allowing transmission of light ofa predetermined wavelength and absorbing light of other wavelengths. Thecolor filters 32 of three colors are provided, which includes thoseselectively transmitting light of R(Red)-wavelength, those selectivelytransmitting light of G(Green)-wavelength and those selectivelytransmitting light of B(Blue)-wavelength. The color filters 32 of R, Gand B are arranged, for example, in this order along the extendingdirection of the gate wiring lines 27 shown in FIG. 2, so that thecolors of adjacent color filters 32 differ from each other.

A light blocking layer 33 (black matrix) is provided between adjacentcolor filters 32 of different colors, so that light from neighboringcolor filters 32 can be blocked. Thus, color mixture is prevented. Thelight blocking layer 33 is arranged in a grid pattern so as to surroundeach color filer 32. An opposite electrode 34, which is formed of thesame ITO as the pixel electrodes 25, for example, is provided on theinside surfaces of the color filters 32.

Ribs 35 (corresponding to a convex portion, a protruding portion or anuneven portion) are provided on the inner surface side of the oppositeelectrode 34. Specifically, the ribs 35 protrude from the inside surfaceof the opposite electrode 34 toward the opposed array substrate 19 side,so as to form an elongated ridge having a predetermined width. As shownin FIG. 2, each rib 35 is V-shaped when viewed from the top, and islocated alongside at a substantially intermediate position between slits31 which are arranged adjacent to each other on the array substrate 19side. Each rib 35 is arranged so that its axial direction issubstantially parallel to the extending direction of the slits 31. Analignment film 36 for directional alignment of the liquid crystal 20 isprovided on the inner surface sides of the opposite electrode 34 and theribs 35 (i.e., provided between the liquid crystal 20 and the oppositeelectrode 34 or the ribs 35). By the uneven portions formed on thesurface of the alignment film 36 due to the ribs 35 protruding from theopposite electrode 34, the alignment of the liquid crystal molecules iscontrolled so that they form an angle with the vertical direction inFIG. 3 (i.e., with the direction perpendicular to the surfaces of thesubstrates 18, 19). Consequently, a rubbing process conventionallyperformed for the alignment film 36 can be eliminated.

The alignment film 36 is formed of a so-called vertical alignment typematerial (e.g., polyimide) similarly to the alignment film 30 on thearray substrate 19 side, so as to align the liquid crystal molecules ina direction perpendicular to the surface of the alignment film 36 when avoltage is not applied to the liquid crystal 20. The film thickness ofthe alignment film 36 is set to about 100 nm to 200 nm, for example. Inthe present embodiment, the opposite electrode 34 and the ribs 35 arethus provided as the underlying base for the alignment film 36. However,in a liquid crystal panel having another stack structure, a layerprovided as the underlying base may differ from the above.

In the liquid crystal panel 11 having the above-described construction,defects may be developed on the alignment film 30 or 36 during amanufacturing process. The defects include a foreign substance defect,i.e., adhesion of a foreign substance X to the alignment film 30, 36,and further include a pinhole defect, i.e., a pinhole H (a filmdefective part) locally formed on the alignment film 30, 36. In thepresent embodiment, an alignment film 30, 36 after the film formingprocess is inspected for the presence and type of a defect. If a defectis then found, the position of the defect is detected, and the defect isrepaired. An inspection/repair apparatus 40 will be hereinafterexplained, which has an inspection function for checking for thepresence of a defect, a position detection function for detecting theposition of the defect, and a repair function for repairing the defect.

The inspection/repair apparatus 40 generally includes an inspectionsection 41 and a repair section 42. As shown in FIGS. 4 and 5, theinspection section 41 includes a conveyer 43 (corresponding to aconveyer means or a conveyer device) for conveying a CF substrate 18 oran array substrate 19 after the film forming process, a rotary encoder44 (corresponding to a drive state detection means or a drive statedetection device for the conveyer means) disposed on the drive sectionof the conveyer 43 for detecting the drive state of the drive section, aline sensor 45 (corresponding to an imaging means or an imaging device)for imaging the surface of the conveyed substrate 18, 19, and a defectdetection circuit 46 for processing signals outputted from the rotaryencoder 44 or the line sensor 45.

On the other hand, the repair section 42 includes a drive circuit 47that receives defect position information outputted from the defectdetection circuit 46. Further included are a UV radiation head 48(corresponding to an ultraviolet radiator, a surface modification meansor a surface modification device) and a transfer head 49 (correspondingto a transfer means or a transfer device), which are provided forrepairing a defect based on signals outputted from the drive circuit 47.

The inspection section 41 will be described in detail. The conveyer 43can convey the substrate 18, 19 in its long-side direction and with apredetermined speed, while holding it in a horizontal position. Therotary encoder 44 can output a pulse signal to the defect detectioncircuit 46, based on the drive state of the drive section of theconveyer 43. Alternatively, the substrate 18, 19 may be conveyed in itsshort-side direction.

In the line sensor 45, a number of light receiving elements are linearlyarranged so that the array direction of the light receiving element isperpendicular to the conveying direction (main scanning direction) ofthe substrate 18, 19 on the conveyer 43 and is parallel to thehorizontal direction. The array direction of the light receivingelements corresponds to the secondary scanning direction. The linesensor 45 can image the surface condition of the substrate 18, 19, andoutput light sensitive signals from the respective light receivingelements to the defect detection circuit 46.

The defect detection circuit 46 can detect the presence, type andposition of a defect based on the pulse signal from the rotary encoder44 and the light sensitive signals from the line sensor 45. The defectdetection circuit 46 determines the presence and type of a defect, forexample, by comparing the surface conditions of adjacent pixels based onthe light sensitive signals from the line sensor 45, and therebyclassifying pixels into those corresponding to non-defective areas,those corresponding to a foreign substance defect and thosecorresponding to a pinhole defect. On the other hand, in order todetermine the position of a defect, the position of the defect in themain scanning direction is detected based on the pulse signal from therotary encoder 44 while the position of the defect in the secondaryscanning direction is detected based on the light sensitive signals fromthe line sensor 45, resulting in obtaining two-dimensional (i.e.,X-directional and Y-directional) position information of the defect onthe substrate 18, 19. In the case that a foreign substance defect isdetected, a process for removing the foreign substance X is performed,during which a portion of the alignment film 30 or 36, as well as theforeign substance X, is removed so as to form a pinhole H (i.e., a filmdefective part).

Next, the repair section 42 will be described in detail. The drivecircuit 47 can move the UV radiation head 48 and the transfer head 49 inX-, Y-, and Z-directions, based on the defect position informationoutputted from the defect detection circuit 46.

Based on a signal from the drive circuit 47, the UV radiation head 48 ismoved to the position of a pinhole H formed on the substrate 18, 19. TheUV radiation head 48 includes a Xe2 excimer lamp as a light source,which can radiate excimer UV light (vacuum ultraviolet light) having acenter wavelength of 172 nm. Due to the excimer UV light, the organicmatters adhering to the surface of the substrate 18, 19 on which thepinhole H is developed (i.e., adhering to the surface of any pixelelectrode 25 or the insulating layer 29 on the array substrate 19, oradhering to the surface of the opposite electrode 34 or any rib 35 onthe CF substrate 18) can be destructed and removed. Thus, the so-calleddry cleaning can be achieved. Alternatively, a mercury lamp (centerwavelength: 180 nm-400 nm), a KrF excimer laser (wavelength: 248 nm), anArF excimer laser (wavelength: 193 nm), or a Kr2 excimer lamp (centerwavelength: 146 nm) may be used as the light source of the UV radiationhead 48, for example. A light source that radiates ultraviolet lighthaving a wavelength (center wavelength) of 146 nm to 365 nm ispreferable for the UV radiation head 48. Obviously, a light source otherthan the above (such as a light source that radiates ultraviolet lightother than excimer UV light) can be used. Further preferably, the lightsource can radiate quasi-monochromatic light having a short centerwavelength (i.e., a wavelength equal to or less than 200 nm). This typeof light source results in increase in energy conversion efficiency andsuppression of heat damage of irradiated portions.

Based on a signal from the drive circuit 47, the transfer head 49 ismoved to the position of the pinhole H formed on the substrate 18, 19.An alignment film repair filler 50 is attached to the transfer head 49,and therefore the alignment film repair filler 50 can be transferred tothe pinhole H by pressing the transfer head 49 to the pinhole H (SeeFIG. 10 or 16). Specifically, the transfer head 49 is formed of a porousmaterial having flexibility, so as to be capable of absorbing andcontaining a predetermined amount of alignment film repair filler 50therein and further capable of elastic deformation. The alignment filmrepair filler 50 is formed by dissolving an alignment film material(e.g., polyimide) in solvent. The support shaft 49 a for supporting thetransfer head 49 is made of glass, for example, so that the alignmentfilm repair filler 50 cannot easily travel from the transfer head 49 tothe support shaft 49 a.

As shown in FIG. 6, the transfer head 49 after finishing the repair (ortransfer operation) waits while being held in a container (correspondingto a dryness prevention means or a dryness prevention device) in whichan alignment film repair filler 50 is stored. In the container 51, thealignment film repair filler 50 is consistently supplied to the transferhead 49. Thereby, drying of the surface of the waiting transfer head 49due to evaporation of the solvent of the alignment film repair filler 50from the surface can be prevented.

This is the end of explanation for the construction of the presentembodiment. Next, the operation thereof will be explained. When aprocess for forming an alignment film 30 or 36 is completed, thesubstrate 18 or 19 is conveyed to the inspection/repair apparatus 40.During an inspection process (that includes a position detectionprocess), while the substrate 18, 19 is conveyed by the conveyer 43 asshown in FIG. 4, the surface condition thereof is imaged by the linesensor 45. At the time, a pulse signal that is from the rotary encoder44 disposed on the drive section of the conveyer 43 and is based on thedrive state, and light sensitive signals from the line sensor 45 areinputted to the defect detection circuit 46, as shown in FIG. 5.

The defect detection circuit 46 detects the presence, type and positionof a defect (i.e., a foreign substance defect or a pinhole defect) basedon the above two kinds of signals. If a defect has not been found, thesubstrate 18, 19 is conveyed to the next stage of the manufacturingprocess without being conveyed to the repair process. If a defect hasbeen found, the substrate 18, 19 is conveyed to a foreign substanceremoval process when the type thereof is a foreign substance defect. Inthe case of a pinhole defect, the substrate 18, 19 is conveyed to therepair process.

When a foreign substance defect is detected as shown in FIG. 7, theforeign substance X is removed using a removal tool such as a needle. Atthe time, a portion of the alignment film 30, 36, as well as the foreignsubstance X, will be removed, resulting in a pinhole H formed at aposition from which the foreign substance X is removed. The substrate18, 19 after the removal of the foreign substance X is conveyed to therepair process, which will be hereinafter explained.

In the repair process, the pinhole H formed on the alignment film 30, 36is repaired. The concrete description will be made on the case where apinhole H is formed as shown in FIG. 8 on the alignment film 36 on theCF substrate 18, for example, so that a flat exposed area of theunderlying base (e.g., the opposite electrode 34 in FIG. 8) of thealignment film 36 is provided through the pinhole H. First, the UVradiation head 48 is moved and positioned by the drive circuit 47 so asto be aligned with the pinhole H. Then, the pinhole H is irradiated withexcimer UV light from the UV radiation head 48 for a predeterminedduration, so that the organic matters adhering to the exposed surface ofthe underlying base provided through the pinhole H is destructed andremoved. Thus, a surface modification process is performed, and therebyadhesion of the underlying base to the alignment film repair filler 50(or wettability thereof) is improved.

After the surface modification process is completed, the transfer head49 is moved and positioned by the drive circuit 47 so as to be alignedwith the cleaned pinhole H, as shown in FIG. 9. Then, the transfer head49 is pressed to the pinhole H for a predetermined duration, as shown inFIG. 10. When the transfer head 49 is thereafter raised up, thealignment film repair filler 50 on the transfer head 49 is transferredto the substantially entire area of the pinhole H, as shown in FIG. 11.At the time, the alignment film repair filler 50 can easily adhere tothe pinhole H, due to the foregoing dry cleaning. The film thickness ofthe repair part 52 can be adjusted to conform to the surroundingalignment film 36, by controlling the duration time and/or the pressureintensity when the transfer head 49 is pressed against the pinhole H.Further, the film thickness of the repair part 52 can be also adjustedby controlling the density of the alignment film repair filler 50. Thetransfer head 49 after finishing the transfer is placed in the container51 shown in FIG. 6.

Next, explanation will be made on the case where a pinhole H is smallerthan the transfer head 49 in size. In this case, as shown in FIG. 12,the transfer head 49 is applied so as to reach the alignment film 36around the pinhole H, when the transfer head 49 is pressed against thepinhole H. At the time, the transfer head 49 elastically deforms so asto conform to steps formed between the pinhole H and the alignment film36, and thereby can be tightly applied to the pinhole H and thealignment film 36. When the transfer head 49 is raised up afterfinishing the transfer, a repair part 52 is formed on the surroundingalignment film 36 as well as on the pinhole H, as shown in FIG. 13. Thealignment film repair filler 50 is thus applied on the alignment film36, which will cause no problem. However, an additional process forselectively removing the alignment film repair filler 50 applied on thealignment film 36 may be thereafter performed, so as to flatten therepair part 52.

Next, explanation will be made on the case where a pinhole H is formedas shown in FIG. 14 on the alignment film 30 on the array substrate 19,for example, so that an uneven exposed area of the underlying base(e.g., the pixel electrode 25 and the insulating layer 29 in FIG. 14) ofthe alignment film 30 is provided through the pinhole H. In this case,the organic matters adhering to the surface of the underlying baseshould be also destructed and removed by radiating excimer UV light fromthe UV radiation head 48 to the pinhole H, as in the above case with theCF substrate 18.

Thereafter, the transfer head 49 is positioned to be aligned with thepinhole H as shown in FIG. 15. Then, as shown in FIG. 16, the transferhead 49 is pressed against the pinhole H for a predetermined duration.At the time, the transfer head 49, made of a porous material havingflexibility, elastically deforms so as to conform to the step-like shapeof the underlying base, and thereby has intimate contact with thepinhole H with substantially no space therebetween. When the transferhead 49 is thereafter raised up, the alignment film repair filler 50 istransferred to the substantially entire area of the pinhole H, as shownin FIG. 17. The film thickness of the repair part 52 can be adjusted toconform to the alignment film 30 by controlling the duration time and/orthe pressure intensity when pressing the transfer head 49 or bycontrolling the density of the alignment film repair filler 50, as inthe above case with the alignment film 36 on the CF substrate 18 side.If the pinhole H is smaller than the transfer head 49 in size, therepair thereof can be achieved in a similar manner to the case with thealignment film 36 on the CF substrate 18 side.

The film thickness of the repair part 52 is most preferably set tocorrespond to that of the alignment film 30, 36, but cannot necessarilycorrespond thereto. In any case, it is preferable that the thickness ofthe repair part 52 is set to be equal to or smaller than 200 nm,independently of the film thickness of the alignment film 30, 36. Thevoltage value, applied as an assignment to the liquid crystal layer whena voltage is applied between the pixel electrodes 25 and the oppositeelectrode 34, depends on the film thicknesses of the alignment film 30,36 and the repair part 52. When the film thickness of the repair part 52is larger than 200 nm, for example, an insufficient voltage is appliedas an assignment to the liquid crystal layer at a pixel associated withthe repair part 52, which may cause a display failure. If the filmthickness of the repair part 52 is set to be equal to or smaller than200 nm as in the present embodiment, a sufficient voltage can be appliedto the liquid crystal layer, resulting in excellent display performance.At the same time, the film thickness of the repair part 52 is preferablyset to be equal to or larger than 50 nm, independently of the filmthickness of the alignment film 30, 36. Thereby, an excess voltage canbe prevented from being applied as an assignment to the liquid crystallayer when a voltage is applied as described above. Further, thealignment control for the liquid crystal molecules can be adequatelyachieved, so that a high stability in alignment of the liquid crystalmolecules is maintained, resulting in excellent display performance.This is particularly effective in the case where alignment films 30, 36of a vertical alignment type that induce a large pretilt angle are usedas in the present embodiment.

After pinholes H are thus repaired, the array substrate 19 and the CFsubstrate 18 are attached to each other, and liquid crystal 20 isdisposed therebetween. Thereafter, polarizing plates 22, 23 are appliedto the outer surface sides of the respective substrates 18, 19. Thus,the liquid crystal panel 11 shown in FIG. 3 is fabricated. In the liquidcrystal panel 11, the repair part 52 having a film thicknesscorresponding to that of the alignment film 30, 36 is formed on thepinhole H developed on the alignment film 30, 36. Thereby, excellentdisplay performance can be obtained. Obviously, the pinhole H is notlimited to those shown in the figures, but rather can have any othersize and/or any other shape and can be developed at any position on thesubstrate 18, 19.

As stated above, according to the present embodiment, the alignment film30, 36 is inspected for the presence of a pinhole H, and the position ofthe pinhole H is detected. Then, the pinhole H is repaired by applyingan alignment film repair filler 50 to the pinhole H. Thereby, the yieldrate can be improved, compared to the conventional case where analignment film including a pinhole is re-formed, for example.Consequently, the manufacturing cost can be reduced.

In the repair process, a stamping technique is used so that thealignment film repair filler 50 is transferred to the pinhole H from thetransfer head 49 on which the alignment film repair filler 50 isattached. Consequently, the film thickness of the repair part 52 can bereadily adjusted, compared to the case where a technique for droppingdroplets of an alignment film repair filler into a pinhole is used in arepair process, for example.

In the repair process, the transfer of the alignment film repair filler50 is achieved by pressing the transfer head 49, on which the alignmentfilm repair filler 50 is attached, against the pinhole H. Therefore, thefilm thickness of the repair part 52 can be readily adjusted bycontrolling the duration time and/or the pressure intensity when thetransfer head 49 is pressed against the pinhole H. Further, alocally-developed pinhole H can be readily repaired, compared to thecase where the transfer of an alignment film repair filler is achievedby a transfer roller, for example.

The alignment film repair filler 50 is formed by dissolving an alignmentfilm material in solvent, and the waiting transfer head 49 afterfinishing the repair is immersed in the alignment film repair filler 50in the container 51. Thereby, drying of the surface of the transfer head49 due to evaporation of the alignment film repair filler 50 can beprevented.

The transfer head 49 is made of a porous material having flexibility,and thereby the film thickness of the repair part 52 can be furtherreadily adjusted. Further, the alignment film repair filler 50 can bereliably attached to the pinhole H due to deformation of the flexibletransfer head 49, even if a stepped area is provided around the pinholeH.

The surface modification process is performed before the repair process,in order to facilitate adhesion of the alignment film repair filler 50to the pinhole H. Thereby, the repair can be reliably achieved.

In the surface modification process, the UV radiation head 48 radiatesexcimer UV light (ultraviolet light) to the pinhole H. Thereby, thesurface modification can be suitably achieved. Further, the processingtime can be reduced, compared to the case where the surface modificationis achieved by a wet process, for example.

The wavelength of light radiated from the UV radiation head 48 is set tobetween 146 nm and 365 nm. Thereby, the surface modification can befurther suitably achieved.

The alignment films 30, 36 of the liquid crystal panel 11 have afunction for aligning the liquid crystal molecules in a directionsubstantially perpendicular to the surfaces of the alignment films 30,36 when a voltage is not applied to the liquid crystal 20. Therefore,adhesion of the alignment films 30, 36 to the substrates 18, 19 may bedegraded, and a pinhole H can be easily formed during the manufacturethereof. However, an alignment film repair filler 50 can be applied tothe pinhole H so as to form a repair part 52. Thus, the pinhole H can berepaired so that the yield rate is effectively improved.

The ribs 35 or slits 31 for alignment control of the liquid crystal 20are formed on the surface of the substrate 18 or 19 of the liquidcrystal panel 11, so that the alignment film 36 or 30 is formed alongthe ribs 35 or the slits 31. Consequently, a larger area of thesubstrate 18, 19 may be covered with the alignment film 36, 30, andtherefore a pinhole H can be easily formed. However, an alignment filmrepair filler 50 can be applied to the pinhole H so as to form a repairpart 52. Thus, the pinhole H can be repaired so that the yield rate iseffectively improved.

The film thickness of the repair part 52 is adjusted to between 50 nmand 200 nm, and thereby excellent display performance can be obtained.

Other Embodiments

The present invention is not limited to the embodiment explained in theabove description made with reference to the drawings. The followingembodiments may be included in the technical scope of the presentinvention, for example.

(1) Instead of the line sensor, other types of imaging means such as anarea sensor may be used in the inspection process.

(2) In the inspection process, the substrate may be fixed, and the linesensor may be moved instead. In this case, the rotary encoder should bedisposed on the drive section provided for driving the line sensor, sothat a pulse signal from the rotary encoder is outputted to the defectdetection circuit.

(3) The inspection/repair apparatus may include a foreign substanceremoval section, so that the removal operation for a foreign substancecan be automatically performed when a foreign substance defect has beenfound in the inspection process.

(4) The line sensor may be eliminated from the inspection process sothat a personnel detects pinholes with a microscope, for example.Alternatively, the inspection may be performed with a combination of aline sensor and a microscope.

(5) In the above embodiment, the inspection for the presence of apinhole defect or a foreign substance defect and the detection of theposition thereof are simultaneously performed in the inspection process(i.e., the inspection process includes the position detection process).However, the position detection process may be performed separately fromthe inspection process. Further, detection of a foreign substance defectmay be eliminated from the inspection process, so that detection of apinhole defect is solely performed. Conversely, a defect other than aforeign substance defect or a pinhole detect may be concurrentlydetected in the inspection process.

(6) In the surface modification process, wet cleaning may be performedinstead of the dry cleaning.

(7) In the surface modification process, the UV radiation head may befixed, and the light radiated therefrom may be reflected by a movablemirror, for example, so as to be applied to a target pinhole.

(8) In the surface modification process, the UV radiation head mayradiate light at a wavelength out of the range of 146 nm to 365 nm(i.e., at a wavelength equal to or less than 146 nm, or equal to orlarger than 365 nm), which can be also included in the presentinvention.

(9) In the repair process, a transfer head made of a material other thanporous materials may be used.

(10) In the repair process, instead of applying an alignment film repairfiller on the entire area of a pinhole, the alignment film repair fillermay be applied to only a portion of the pinhole as long as improvementin display performance can be expected.

(11) Instead of the transfer head, a transfer roller may be used in therepair process for applying an alignment film repair filler to apinhole.

(12) In the above embodiment, the liquid crystal panel, in which analignment film material of vertical alignment type is used, isillustrated. However, the present invention can be also applied toconstructions in which another type of alignment film material is used,such as a construction in TN mode, ECB mode or horizontal alignmentmode.

(13) In the above embodiment, the liquid crystal panel, in which theribs and slits provided as structures for alignment control of theliquid crystal, is illustrated. However, the present invention can bealso applied to a liquid crystal panel in which the foregoing structuresfor alignment control are not provided.

(14) The present invention can be also applied to a construction thatincludes an alignment film having a film thickness out of the range of100 nm to 200 nm (i.e., a thickness equal to or less than 100 nm, orequal to or larger than 200 nm).

(15) The repair part may have a film thickness out of the range of 50 nmto 200 nm (i.e., equal to or less than 50 nm, or equal to or larger than200 nm), which can be also included in the present invention.

1. In a process of manufacturing a display panel in which liquid crystalis disposed between a pair of substrates arranged opposite to each otherand a vertical alignment type alignment film for aligning molecules ofthe liquid crystal in a direction perpendicular to surfaces of thesubstrates is provided on at least one of the substrates, a displaypanel manufacturing method comprising: inspecting the vertical alignmenttype alignment film for a presence of a film defective part by aninspection process; detecting a position of the film defective part by aposition detection process; and repairing the film defective part byattaching an alignment film repair filler to an exterior surface of atransfer head and by pressing the transfer head to the film defectivepart.
 2. A display panel manufacturing method as in claim 1, furthercomprising: forming an uneven portion for alignment control of themolecules of the liquid crystal on the substrate; and forming thevertical alignment type alignment film on a surface of the substratehaving the uneven portion, wherein the transfer head has elasticflexibility and is pressed to the film defective part formed on theuneven portion so as to elastically deform to conform the uneven portionand the alignment film repair filler is transferred to the filmdefective part in the repairing process.
 3. A display panelmanufacturing method as in claim 1, wherein a film thickness of the filmdefective part to which the alignment film repair filler is transferredby the transfer head is set to between 50 nm and 200 nm.
 4. A displaypanel manufacturing method as in claim 1, wherein the transfer head isformed of a porous material having flexibility.
 5. A display panelmanufacturing method as in claim 1, further comprising: detecting aforeign substance defect; and removing the foreign substance defect. 6.A display panel manufacturing method as in claim 1, wherein thealignment film repair filler is formed by dissolving a verticalalignment type alignment film material in solvent, and the transfer headafter finishing repair waits while being immersed in the alignment filmrepair filler .
 7. A display panel manufacturing method as in claim 1,wherein a surface modification process for facilitating adhesion of thealignment film repair filler to the film defective part is performedbefore the repair process.
 8. A display panel manufacturing method as inclaim 1, wherein ultraviolet light is radiated to the film defectivepart in the surface modification process.
 9. A display panelmanufacturing method as in claim 8, wherein the ultraviolet light isradiated at a wavelength of 146 nm to 365 nm.
 10. A display panelmanufacturing apparatus for a display panel in which liquid crystal isdisposed between a pair of substrates arranged opposite to each other, avertical alignment type alignment film is provided on an opposed surfaceof the substrates, said display panel manufacturing apparatuscomprising: an inspection device arranged to inspect the verticalalignment type alignment film for a presence of a film defective part; aposition detection device arranged to detect a position of the filmdefective part; and a filler application device arranged to apply analignment film repair filler to at least a portion of the film defectivepart so as to repair the film defective part, wherein said fillerapplication device is a transfer head to which said alignment filmrepair filler is attached and pressed to the film defective part so asto transfer the alignment film repair filler to the film defective part.11. A display panel manufacturing apparatus for a display panel havingan uneven portion as in claim 10, wherein said transfer head has elasticflexibility and is pressed to the film defective part formed on theuneven portion so as to elastically deform to conform the uneven portionand said alignment film repair filler is transferred to the filmdefective part.
 12. A display panel manufacturing apparatus as in claim10, wherein said filler application device sets a film thickness of thefilm defective part to which said alignment film repair filler istransferred by said transfer head to between 50 nm and 200 nm.
 13. Adisplay panel manufacturing apparatus as in claim 10, wherein saidtransfer head is formed of a porous material having flexibility.
 14. Adisplay panel manufacturing apparatus as in claim 10, further comprisinga foreign substance removal device, wherein: said inspection devicedetects a foreign substance defect; said position detection devicedetects a position of the foreign substance defect; and said foreignsubstance removal device removes the foreign substance defect.
 15. Adisplay panel manufacturing apparatus as in claim 10, further comprisinga dryness prevention device, by which said alignment film repair fillerformed by dissolving a vertical alignment type alignment film materialin solvent is stored, and which is capable of containing said transferhead that is waiting after finishing repair.
 16. A display panelmanufacturing apparatus as in claim 10, further comprising a surfacemodification device arranged to modify a surface of the film defectivepart in order to facilitate adhesion of said alignment film repairfiller to the film defective part.
 17. A display panel manufacturingapparatus as in claim 16, wherein said surface modification deviceincludes an ultraviolet radiator arranged to radiate ultraviolet lightto the film defective part.
 18. A display panel manufacturing apparatusas in claim 17, wherein said ultraviolet radiator is capable ofradiating the ultraviolet light at a wavelength of 146 nm to 365 nm.